Thanks for the information - I just filed a bug report:
https://forum.paradoxplaza.com/forum/index.php?threads/cities-skylines-steam-floating-shaders-for-ferries-are-not-working-for-workshop-assets.1064857/

I've checked ferries by 3 other authors and none of them have the water effects.

I believe it's something Colossal Orders may have left out in the template. Hopefully, they can add the effect back in and I can update these ships agin.

Hi,
I really like your updated ship series! However I noticed, they do not behave as the default vanilla ships - the water floating shaders are not working, so it doesn't look like they are swimming in the water it looks like they are "driving" on top of water like on a road.
Is there something that can be done against that?
Best regards!